The embodiment relates to a wireless power transmitter, a wireless power receiver and a wireless power transmission method.
A wireless power transmission or a wireless energy transfer refers to a technology of wirelessly transferring electric energy to desired devices. In the 1800's, an electric motor or a transformer employing the principle of electromagnetic induction has been extensively used and then a method for transmitting electrical energy by irradiating electromagnetic waves, such as radio waves or lasers, has been suggested. Actually, electrical toothbrushes or electrical razors, which are frequently used in daily life, are charged based on the principle of electromagnetic induction. Until now, the long-distance transmission using the magnetic induction, the resonance and the short-wavelength radio frequency has been used as the wireless energy transfer scheme.
Recently, among wireless power transmitting technologies, an energy transmitting scheme using resonance has been widely used.
Since an electric signal generated between the wireless power transmitter and the wireless power receiver is wirelessly transferred through coils in a wireless power transmitting scheme using resonance, a user may easily charge electronic appliances such as a portable device.
In addition, the wireless power transmitter may receive information about a state of a wireless power receiver to transmit power. A load modulation technique is used for data transmission since high cost is required if an additional communication channel or an additional communication unit is provided for the data transmission from the wireless power receiver to the wireless power transmitter. The load modulation technique is a scheme that senses a variation of input impedance of a wireless power transmitter party when a load (impedance) of the wireless power receiver is changed.
However, an application of the load modulation technique is limited to a magnetic induction type wireless power transmission system.